Migraine is a primary headache disorder that may be characterized by unilateral throbbing pain which worsens with head movement. This can be associated with other symptoms including nausea, light and noise sensitivity, lacrimation, nasal congestion, and rhinorrhea. An array of factors can trigger migraine headache, such as internal changes (hormonal changes, stress, sleep deprivation) or external changes (weather changes, alcohol, flickering light).
In some cases, a migraine attack begins with a premonitory visual aura. These patients experience a visual disturbance in the form of a zigzag spectrum around a blind spot, which grows in size over a 20-30 min period. This visual effect is known as the “fortification spectrum.” The development of the fortification spectrum over time has been shown to correspond to a wave of depression in the activity of cortical neurons, which typically begins in the occipital lobe, and spreads anteriorly. The establishment of this correspondence has permitted the elaboration of a theory about the pathophysiological changes that may cause migraine and other headaches.
As neurons depress, they release nitric oxide (NO), which triggers the dilation of meningeal blood vessels. This vasodilation can result in a dull headache, which corresponds to the earliest phase of migraine.
The dilation of the meningeal blood vessels increases the activity of the nerve endings of the primary afferent neurons of the trigeminal nerve that are wrapped around them. As a result, the trigeminal cells release calcitonin gene related protein (CGRP), a vasodilator neuropeptide which further increases the dilation of the meningeal blood vessels, and further feeds into the trigeminal nerve activation. The local intracranial increased activation of the trigeminal nerve spreads through the trigeminal ganglion into the Trigeminal Nucleus Caudalis (TNC) in the brainstem in a process known as peripheral sensitization. The activation of the TNC leads in turn to a central activation process, through its thalamic and cortical projections, which are illustrated in FIG. 1.
Although the pain associated with migraine involves input from meningeal arteries, activation of the TNC may result in referred pain anywhere along the trigeminal network, including the temporal arteries and temporal muscles. The trigeminocervical network involved in the pathophysiology of migraine contains the three main branches of the trigeminal nerve: the ophthalmic branch (V1), the maxillary branch (V2), and the mandibular branch (V3), as illustrated in FIG. 2; as well as the sensory nerves for the posterior head and neck (C2, C3, C4, C5) that feed into the TNC. A detailed anatomical map of the relevant pathways can be found in pages 316, 317, 600, 601 and 736 of Agur, A. M. R. and Dalley II, A. F. (2005) Atlas of Anatomy 11th Ed., Lippincottt Williams & Wilkins, Philadelphia, which is hereby incorporated by reference.
The activation of the TNC in the brainstem can further spread to the occipital nerve by virtue of its anatomical connection to the TNC, leading to pain sensation in the occipital area.
The activation of the TNC can also spread to the parasympathetic system, by activation of a nearby nucleus in the brainstem, the Superior Salivatory Nucleus (SSN), which is connected to the nucleus caudalis through a network of interneurons, as shown in FIG. 3.
Neurons from the SSN synapse with the Sphenopalatine ganglion, which provides vasomotor innervation to blood vessels and secretomotor innervation to the lacrimal glands, nasal and sinus mucosa. When the parasympathetic system is activated, the upper respiratory tract symptoms associated with migraine occur including, potentially, nasal symptoms (rhinorrhea, and post nasal drip), ocular symptoms (conjunctival injection, and tearing) and sinus congestion (pain or pressure around the sinuses). Other parasympathetic projections further aggravate the cascade of events, like the Sphenopalatine ganglion afferents that innervate the meningeal blood vessels. Activation of the parasympathetic system during a migraine attack is also accompanied by a significant increase in the levels of Vasoactive Intestinal Polypeptide (VIP), a parasympathetic neurotransmitter which causes vasodilation and can be measured in high concentrations during a migraine in the jugular venous drainage.
The increased activity of the trigeminal, occipital and parasympathetic systems just described is common to the so-called Trigeminal Autonomic Cephalgias (TAC), which include Cluster headache, Paroxysmal Hemicrania, SUNCT Syndrome, and Hemicrania Continua.
Cluster headaches are a primary headache disorder involving attacks of less than 3 hours of duration with severe unilateral peri-orbital and temporal pain. These headaches can be associated with lacrimation, nasal congestion, rhinorrhea, conjunctival injection and a Homer's syndrome. The attacks occur in distinct clusters. Cluster headaches typically involve a series of disabling attacks on a daily basis lasting for months at a time. This pattern recurs annually or biannually.
Paroxysmal hemicrania is a primary headache disorder involving frequent attacks of unilateral, peri-orbital and temporal pain typically lasting less than 30 minutes. The pain can be associated with conjunctival injection, lacrimation, nasal congestion, rhinorrhea, ptosis and eyelid edema.
SUNCT Syndrome is a primary headache disorder characterized by multiple attacks of unilateral, peri-orbital and temporal pain typically lasting less than 2 minutes. The pain is associated with conjunctival injection, lacrimation, nasal congestion, rhinorrhea, and eyelid edema. This headache may be associated with trigeminal neuralgia.
Hemicrania Continua is a primary headache disorder characterized by a strictly unilateral headache responsive to Indomethacin. The pain is associated with conjunctival injection, lacrimation, nasal congestion, rhinorrhea, ptosis, and eyelid edema.
The trigeminal nerve is involved in the pain sensations for all of these headache types, as well as headaches triggered by other pathologies. For example, Temporal Arteritis involves inflammation of the temporal artery with painful palpable nodules along the artery. In addition to headache in the temporal area, Temporal Arteritis causes vision loss and jaw pain.
Headaches can also be associated with ischemic stroke. In a stroke, a lack of blood supply to brain tissue causes a sudden localized neurological deficit. In a large number of affected patients, occlusion of the arteries is due to the presence of atherosclerotic plaques in the arteries supplying the brain, for example, the carotid artery and the vertebral basilar artery. The atherosclerotic plaques are often associated with inflammation which further contributes to occlusion of the blood vessel.
Nociceptive fibers stimulated by inflammatory mediators in infectious or allergic rhinitis can also activate the trigeminal brainstem nucleus and precipitate migraine.
TAC and Migraine are difficult to treat. Numerous medications have been used to prevent Cluster and Migraine headaches from occurring, which include, amongst others: Propranolol, Timolol, Divalproex Sodium, Topiramate, Verapamil, Indomethacin and Amitriptyline. These medicines have numerous side effects and patients are poorly compliant with them. In the case of TAC, Indomethacin, in particular, is difficult for patients to tolerate due to gastro-intestinal upset.
All of the headache disorders described above produce disability and better treatment modalities are needed.
Recently, Botulinum toxin has been shown to be effective to treat migraine headaches when injected in the face, cranium and neck (Binder, U.S. Pat. No. 5,714,468). Botulinum toxin is a potent polypeptide neurotoxin produced by the gram positive bacterium Clostridium botulinum which causes a paralytic illness in humans termed Botulism. Botulinum toxin has a light and a heavy chain. The heavy chain attaches to a cell surface receptor and the complex is then endocytosed. After endocytosis, the light chain translocates from the endosome into the cytoplasm, where it cleaves a segment of the SNARE protein complex responsible for vesicle fusion in the presynaptic nerve terminal. As a result, the release of neurotransmitters from these vesicles is effectively blocked for 3-6 months.
There are 7 immunologically distinct toxins: A, B, C1, D, E, F and G (Simpson, et al., Pharmacol. Rev., 33:155-188, 1981). These toxins bind to presynaptic membranes of target nerves and appear to work in a similar fashion (Brin, et al., “Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology”, Neurology, 40:1332-1336, 1990). Botulinum toxin shows a high affinity for cholinergic neurons. Botulinum toxin A produces a reversible, flaccid paralysis of mammalian skeletal muscle, presumably by blocking the exocytosis of acetylcholine at peripheral, presynaptic cholinergic receptors (Rabasseda, et al., Toxicon, 26:329-326, 1988). However, flaccid muscular paralysis is not necessary to achieve the reduction or prevention of migraine symptomatology. In fact, headache pain reduction may be observed at dosages of presynaptic neurotoxin which are lower or higher than dosages required to produce flaccid paralysis of skeletal muscle and without introduction of the neurotoxin into muscle tissue (Binder, U.S. Pat. No. 5,714,468).
Although the molecular basis for the sensation of migraine pain is not clear (Goadsby, et al., N. Eng. J. Med., 346:257-270, 2004), Botulinum toxin might exert its analgesic effect by blocking the release of nociceptive and inflammatory agents that are released during migraine, and not by blocking the release of acetylcholine. Because Botulinum toxin does not act on acetylcholine directly, but on the SNARE protein complex that mediates vesicle fusion, the release of other molecules which is also mediated by the SNARE protein complex is also affected by the toxin (Aoki, Current Medicinal Chemistry, 11:3085-3092, 2004). In fact, studies have shown that Botulinum toxin can also block the release of substance P, which is associated with neurogenic inflammation and pain generation (Aoki, Current Medicinal Chemistry, 11:3085-3092, 2004), glutamate, also associated with nociception (Cui, et al., Pain, 107:125-133, 2004), epinephrine, norepinephrine, and calcitonin gene-related peptide (Aoki, Current Medicinal Chemistry, 11:3085-3092, 2004). Botulinum toxin A does not appear to cause degeneration of nervous or muscular tissue and has been approved for use in certain therapies by the U.S. Food and Drug Administration.
In addition to Botulinum toxin A, other presynaptic neurotoxins have also been suggested to be useful for the treatment of migraine, given the functional characteristics they share with Botulinum toxin (Binder, U.S. Pat. No. 5,714,468). One of these presynaptic neurotoxins is Tetanus neurotoxin, which is produced by Clostridium tetani (DasGupta, et al., Biochemie, 71:1193-1200, 1989), and shows significant sequence homology with serotypes A and E of Botulinum toxin. In particular, fragment Ibc of the Tetanus toxin, which is obtained by peptide digestion of the toxin, appears to act peripherally to produce flaccid paralysis (Fedinic, et al., Boll.lst. Sieroter Milan, 64: 35-41, 1985; and, Gawade, et al., Brain Res., 334:139-46, 1985).
Staphylococcal alpha-toxin has also been suggested for therapeutic use. This toxin stimulates the production in the brain of muscle-relaxing factor (MRF), which results in reversible, flaccid paralysis of skeletal muscle (Harshman, et al., Infect. Immun., 62:421-425, 1994). Staphylococcal alpha-toxin may function similarly to Botulinum toxin.
Other toxins which cause reversible, flaccid paralysis are the acylpolyamine toxins, which are anticholinergic, presynaptic neurotoxins produced in the venom of many invertebrates (Herold, et al., Anesthesiology, 77:507-512, 1992). For example, toxins AR636 and AG489 from spiders Argiope aurantia and Agelenopsis aperta lead to motor inhibition at a dosage of 2 micrograms and sensory inhibition at 7 micrograms.
Since the use of presynaptic neurotoxins to treat migraines was initially implemented by administering the toxins in the face, cranium and/or neck (Binder, U.S. Pat. No. 5,714,468), the hypothesis about the physiological changes underlying migraine has been significantly developed. The present invention provides an improvement in the therapeutic and preventive use of Botulinum toxin, among other presynaptic neurotoxins, to treat migraines, TAC and other headaches associated with vascular conditions by using a new method to administer these neurotoxins. The improvement is based on the recent theory that has emerged about the pathophysiological changes triggering these headaches, which involves the trigeminal, occipital and parasympathetic systems and therefore affects the administration sites of the toxins.